In a general sense, the invention is directed to systems and methods for visualizing interior regions of the human body. In a more particular sense, the invention is directed to systems and methods for mapping or ablating heart tissue for treating cardiac conditions.
Systems and methods for visualizing interior regions of a living body are known. For example, ultrasound systems and methods are shown and described in Yock U.S. Pat. No. 5,313,949 and Webler et al. U.S. Pat. No. 5,485,846.
Due to dynamic forces within the body, it can be difficult to stabilize internal imagining devices to consistently generate accurate images having the quality required to prescribe appropriate treatment or therapy. There is often an attendant need to constantly position and reposition the image acquisition element. In addition, tissue and anatomic structures inside the body can contact and occlude the image acquisition element.
External imaging modalities are available. Still, these alternative modalities have their own shortcomings.
For example, in carrying out endocardial ablation procedures, fluoroscopic imaging is widely used to identify anatomic landmarks within the heart. Fluoroscopic imaging is also widely used to locate the position of the ablation electrode or electrodes relative to the targeted ablation site. It is often difficult to identify these anatomic sites using fluoroscopy. It is also difficult, if not impossible, to use fluoroscopy to ascertain that the desired lesion pattern has been created after ablation. Often, the achievement of desired lesion characteristics must be inferred based upon measurements of applied ablation power, system impedance, tissue temperature, and ablation time. Furthermore, fluoroscopy cannot readily locate the border zones between infarcted tissue and normal tissue, where efficacious ablation zones are believed to reside.
The invention provides improved systems and methods that acquire images of interior body regions in conjunction with diagnostic or therapeutic procedures. The systems and methods introduce into the interior body region a catheter tube carrying an imaging element for visualizing tissue. The catheter tube also carries a support structure, which extends beyond the imaging element for contacting surrounding tissue away from the imaging element. The support element stabilizes the imaging element, while the systems and methods operate the imaging element to visualize tissue in the interior body region. The systems and methods resist dislodgment or disorientation of the imaging element, despite the presence of dynamic forces. The support structure also carries a diagnostic or therapeutic component to contact surrounding tissue. In one embodiment, the component comprises a tissue ablation electrode. In another embodiment, the component comprises an electrode to sense electrical events in tissue.
The systems and methods make use of the images obtained by the imaging element for one or more purposes, including (i) orienting the diagnostic or therapeutic component within the interior body region; or (ii) characterizing tissue morphology, including infarcted tissue; or (iii) assessing contact between the diagnostic or therapeutic component and the surrounding tissue; or (iv) viewing a lesion pattern after transmitting ablation energy; or (v) identifying thrombus.
In a preferred embodiment, a steering mechanism moves the imaging element without moving the support structure. The steering mechanism permits the imaging element to acquire image slices so that accurate displays of interior body regions can be generated for viewing and analysis by the physician. Accurate images allow the physician to prescribe the appropriate treatment or therapy.
The invention also provides improved systems and methods that provide enhanced, accurate visualization of interior regions of the heart in connection with the creation of lesions patterns aimed at treating arrhythmias. In a preferred embodiment, the support structure carries one or more electrode elements for contacting heart tissue within the heart. In use, the electrode element is intended to transmit ablation energy to form lesions in heart tissue, transmit pacing energy to heart tissue, or sense electrical impulses to map heart tissue, or all three.
In use, the imaging element may visualize tissue surrounding the one or more electrodes on the support structure. In one embodiment, the imaging element comprises an ultrasonic transducer. In another embodiment, the imaging element comprises a fiber optic assembly. The imaging element allows the physician to (i) orient the support structure with respect to a preselected anatomic site within the heart; or (ii) characterize tissue morphology, including infarcted tissue; or (iii) assess contact between an electrode and the endocardium; or (iv) view a lesion pattern; or (v) identifying thrombus before or after an ablation.
In another preferred embodiment, systems and methods for treating atrial fibrillation use the support structure to carry a plurality of spaced-apart energy transmitting electrodes. The systems and methods introduce the catheter into a heart atrium to place at least some of the electrodes in contact with heart tissue. The systems and methods simultaneously transmit ablating energy from a source through each electrode to generate an additive heating effect between electrodes that forms a continuous lesion pattern in tissue contacted by the electrodes. The systems and methods also manipulate the imaging element to visualize tissue surrounding the support structure. The systems and methods display the image for use by the physician; for example, to orient the multiple electrode support structure with respect to a preselected anatomic site within the heart; or to assess contact between electrodes and tissue; or to view the continuous lesion pattern after transmitting ablation through the multiple electrode support structure; or to characterize tissue morphology; or to identify thrombus; or any combination of the foregoing uses.
In one embodiment, an ablation/imaging catheter includes an elongate tube having a distal tube end that extends within the interior region. A porous electrode structure is mounted to the distal tube end, the porous electrode structure comprising an interior region for receiving a conductive medium. An ultrasonic transducer assembly is housed within the distal tube end.
Other features and advantages of the inventions are set forth in the following Description and Drawings, as well as in the appended claims.